PubMed Health⌕ Search

Biomedical subjects

Y Ni

Publications and source records attributed to Y Ni.

At least 55 records · Page 3Linked to original sources
PubMed1999

Studies on the structures and antigenic properties of rabies virus glycoprotein analogues produced in yeast cells.

We investigated two forms (designated as yGI and yGII) of rabies virus glycoprotein (G) analogues produced in the G cDNA-transfected yeast cells. Molecular weights of yGI and yGII were estimated as 66 and 56 kDa, respectively, according to their relative mobility in SDS-PAGE. Although being produced in large amounts, yGI was present mostly in insoluble forms and hardly extractable with non-ionic detergents. The yGI reacted with polyclonal anti-G antibodies, but did not react with our conformational epitope-specific anti-G monoclonal antibodies (G-MAbs). No protective immunity was induced by yGI in guinea pigs nor in mice. On the other hand, yGII was Triton-soluble, but was only small in amount (at most 1% of total G proteins) and was shown to lack the cytoplasmic domain. The yGII, however, reacted with the G-MAbs and induced protective immunity in guinea pigs as well. When the G-cDNA was expressed in animal cells in culture, a single form (about 66 kDa) of G protein was produced, which displayed similar behaviors as seen in its reactivity with the MAbs and intracellular distribution as seen in the virus-infected cells. These results suggest that most G protein molecules were not processed normally in yeast cells, resulting in abnormal folding and multimer formation, while only a small fraction were occasionally folded normally to have conformational epitopes but were mostly deprived of the C-terminal portion.

Animals↗
PubMed1999

Comparison of iron oxide particles (AMI 227) with a gadolinium complex (Gd-DOTA) in dynamic susceptibility contrast MR imagings (FLASH and EPI) for both phantom and rat brain at 1.5 Tesla.

The goal of the study was to compare, in phantom and normally perfused rat brain tissue, a superparamagnetic iron oxide particle-based contrast agent (AMI 227) with a low-molecular-weight gadolinium chelate, gadolinium tetraazacyclododecanetetraacetic acid (Gd-DOTA), in two susceptibility contrast magnetic resonance imaging (MRI) modes [fast low-angle shot sequence (FLASH) and echoplanar imaging (EPI)]. A phantom consisting of dilution series of both contrast agents was manufactured. Dilutions were obtained with isotonic serum from the available agent solutions (0.5 mmol Gd/mL Gd-DOTA; 350 mumol Fe/mL AMI 227). Eighteen rats were studied. Contrast agent (0.1 mL) was bolus injected in each rat, and dynamic MRI was performed (first pass of the contrast agent) in rat brain. The doses of AMI 227 injected were extrapolated from the phantom experiment: 0.2 mmol/kg body weight of Gd-DOTA and 7, 14, and 28 mumol Fe/kg body weight of AMI 227 were injected. For both sequences, signal-to-noise ratios (S/N) were measured on each tube of the phantom and on rat brain from each image of the dynamic imaging. S/N was plotted versus contrast dilution (phantom) and versus time (rats). In the FLASH sequence, a well-shaped curve (S/N decrease, S/N peak decrease, S/N increase) of the first pass of the contrast agent was demonstrated for Gd-DOTA and for AMI 227 (7 mumol Fe/kg body weight). In the EPI sequence, a well-shaped curve was demonstrated for Gd-DOTA, and a plateau effect was noted for both concentrations of AMI 227. With the FLASH technique, dynamic susceptibility contrast imaging of rat brain can be performed with very low concentrations of AMI 227 compared with the Gd-DOTA concentration (0.2 mmol Gd/kg body weight) used in clinical practice. This could be of interest in perfusion imaging, because it may allow for first-pass susceptibility imaging after administration of a small volume in a narrow bolus.

Animals↗
PubMed1999

Crystallization and preliminary X-ray diffraction studies of the lipopolysaccharide core biosynthetic enzyme ADP-L-glycero-D-mannoheptose 6-epimerase from Escherichia coli K-12.

ADP-L-glycero-D-mannoheptose 6-epimerase is a 240 kDa NAD-dependent nucleotide diphosphosugar epimerase from Escherichia coli K12 which catalyzes the interconversion of ADP-D-glycero-D-mannoheptose and ADP-L-glycero-D-mannoheptose. ADP-L-glycero-D-mannoheptose is a required intermediate for lipopolysaccharide inner-core and outer-membrane biosynthesis in several genera of pathogenic and non-pathogenic Gram-negative bacteria. ADP-L-glycero-D-mannoheptose 6-epimerase was overexpressed in E. coli and purified to apparent homogeneity by chromatographic methods. Three crystal forms of the epimerase were obtained by a hanging-drop vapor-diffusion method. A native data set for crystal form III was collected in-house on a Rigaku R-AXIS-IIC image plate at 3.0 A resolution. The form III crystals belong to the monoclinic space group P21. The unit-cell parameters are a = 98.94, b = 110.53, c = 180.68 A and beta = 90.94 degrees. Our recent results show that these crystals diffract to 2.0 A resolution at the Cornell High Energy Synchrotron Source. The crystal probably contains six 40 kDa monomers per asymmetric unit, with a corresponding volume per protein mass (Vm) of 4.11 A3 Da-1 and a solvent fraction of 70%.

Carbohydrate Epimerases↗
PubMed1999

Specificity and prevalence of natural bovine antimannan antibodies.

Immune responses to the carbohydrate components of microorganisms, mediated both by antibodies and by lectins, are an important part of host defense. In the present experiments, the specificity and presence of natural bovine antibodies against mannan, a common fungal antigen, were examined by enzyme-linked immunosorbent assay (ELISA), using Saccharomyces cerevisiae mannan as an antigen. The results showed that all serum samples from animals of three age groups (newborn, calf, and adult) tested contained antimannan antibodies, and the titer of these antibodies increased significantly in adults. However, titers among individual adult cattle differed widely. Inhibition assays showed that yeast mannan was the strongest inhibitor. D-Mannose exhibited only a minor inhibitory effect at high concentrations. This suggests that most of these antibodies recognize an oligosaccharide-based epitope(s) different from those recognized by lectins. Cattle possess three serum C-type lectins (collectins) capable of recognizing mannan in a calcium-dependent manner. Addition of EDTA to the reaction did not reduce antibody binding, suggesting that the binding of these antibodies to mannan was not affected by the presence of collectin. The antibodies purified from either calf or adult serum by mannan-Sepharose affinity chromatography consisted of mainly immunoglobulin G (IgG) and a smaller amount of IgM. IgG1 was shown to be the dominant antimannan IgG isotype by isotype-specific ELISA. Together, these results demonstrate the production of natural antimannan antibodies in cattle in an age-dependent manner. These antibodies might be involved in defending the host against mannan-containing pathogens as a specific line of defense in conjunction with the innate response by lectins.

Age Distribution↗
PubMed1999

Treatment of epiphora due to insufficiency of lacrimal passage by acupuncture at Jingming.

Since 1995, the authors have employed acupuncture at Jingming (UB 1) with the warming needles to treat epiphora due to insufficiency of lacrimal passages. Of the 68 treated eyes in 42 patients, 28 eyes were cured, 35 improved, and 5 ineffective with a total effective rate of 92.65%; and 12 eyes were cured and 34 improved by only one course of treatment.

Acupuncture Points↗
PubMed1999

[Anti-hemolytic and anti-membranous lipid peroxidation effects of daphnetin].

AIM: To investigate the anti-hemolytic and anti-membranous lipid peroxidation effects of daphnetin. METHODS: The inhibition rates of daphnetin on AQD-induced hemolysis and erythrocytic membranous lipid peroxidation were determined by routine in vitro assay for detecting hemolytic toxicity and by HPLC for detecting membranous lipid peroxidation products. RESULTS: Daphnetin at a range of 10-80 mumol/L inhibited dose-dependently AQD-induced hemolysis and lipid peroxidation by 33.0%-69.2% and 11.9%-58.2%, respectively. CONCLUSION: Daphnetin has anti-hemolytic and anti-erythrocytic membranous lipid peroxidation effects.

Aminoquinolines↗
PubMed1999

[Study on the elements in cosmetics by microwave digestion-iCP-AES I. The determination of Pb, As, Cr, Cd, Sr, Bi and Se in solid state cosmetics].

A safe and effective method for the microwave digestion of solid state cosmetic samples is described. The overall digestion conditions, including pressure, power, acids and time of digestion were evaluated by analysing Pb, As, Cr, Cd, Sr, Bi and Se of routine samples with ICP-AES. This method was applied to the determination of certified materials with good agreement.

Cosmetics↗
PubMed1999

[Determination of electron density in Ar-air mixed coolant gas ICP].

The lateral distribution of electron number density at 0, 2, 5, 10 mm above the load coil in Ar-air mixed coolant gas ICP was measured with Stark broadening method of Hbeta line (486.1 nm) and some of the lateral distribution was converted into radial distribution by Abel inversion under the condition similar to that in the low power Ar-ICP. The results show that the distribution of electron number in Ar-air mixed coolant gas ICP is similar to that in Ar-ICP and exhibit off axis maxima. When a lot of air was added to the coolant, the positions of the off axis maxima would near the axis. The electron number density reached maximum and was higher than that in Air-ICP as 5%-10% air was added to the coolant.

English Abstract↗
PubMed1998

Receptor-independent activation of atrial muscarinic potassium channels in the absence of nucleotides.

The removal of nucleotides from the solution bathing the inner face of excised patches of frog atrial membranes was found to activate muscarinic K+ channels in the absence of agonists. Channel activation was also observed in Mg2+-free solutions and blocked by low (0.1-10 microM) concentrations of GDP or GTP. After full activation was achieved, channel openings were abolished by the application of GDP-bound Galphai2 but were not affected by exogenous Gbetagamma dimers, suggesting that effector activation is a consequence of the liberation of betagamma subunits from endogenous G proteins. The process of channel activation in the absence of nucleotides seems to be receptor-independent, because it is not influenced by muscarinic receptor agonists and antagonists or by treatment with uncoupling agents such as pertussis toxin or N-ethyl maleimide. Taken together, these results suggest that the loss of GDP from the G protein nucleotide binding site promotes its uncoupling from receptors and destabilizes the Galpha(empty)betagamma heterotrimer. Therefore, the nucleotide-free form of G proteins has some of the characteristics of the GTP-bound, activated form.

Animals↗
PubMed1998

Use of serologic testing to assess immune status of companion animals.

At the November 1997 meeting of the AVMA Council on Biologic and Therapeutic Agents, the Council recommended that the JAVMA publish an article on the current status of the use of serologic testing in an effort to assist practitioners who must make decisions regarding vaccination of companion animals (i.e., dogs, cats, and horses). It is anticipated that the peer-reviewed article provided here will be of benefit to veterinarians and will facilitate their attempts to maintain animal health through the knowledgeable use of vaccines.

Animals↗
PubMed1998

Platelet-derived growth factor stimulates protein kinase D through the activation of phospholipase Cgamma and protein kinase C.

Platelet-derived growth factor (PDGF) stimulates protein kinase D (PKD) in a time- and dose-dependent manner. We have used a series of PDGF receptor mutants that display a selective impairment of the binding of SH2-containing proteins (GTPase-activating protein, SHP-2, phospholipase Cgamma (PLCgamma), or phosphatidylinositol 3'-kinase (PI3K)) to show that Tyr-1021, the PLCgamma-binding site, is essential for PKD stimulation by PDGF in A431 cells. We next investigated whether any one of these four binding sites could mediate PKD activation in the absence of the other three sites. F5, a receptor mutant that lacks all four binding sites for GTPase-activating protein, PLCgamma, PI3K, and SHP-2, fails to activate PKD. A panel of single add-back mutants was used to investigate if any one of these four sites could restore signaling to PKD. Of the four sites, only the PLCgamma+ single add-back receptor restored PDGF-mediated activation of PKD, and only this add-back receptor produced diacylglycerol (DAG) in a PDGF-dependent manner. 1,2-Dioctanoyl-sn-glycerol, a membrane-permeant DAG analog, was found to be sufficient for activation of PKD. Taken together, these data indicate that PLCgamma activation is not only necessary, but also sufficient to mediate PDGF-induced PKD activation. Although the presence of a pleckstrin homology domain makes PKD a potential PI3K target, PKD was not stimulated by selective PI3K activation, and wortmannin, an inhibitor of PI3K, did not inhibit PDGF signaling to PKD. The activation of PKD by DAG or by the wild-type and PLCgamma+ add-back PDGF receptors was inhibited by GF109203X, suggesting a role for protein kinase C in the stimulation of PKD by PDGF. PDGF induced a time-dependent phosphorylation of PKD that closely correlated with activation. The PDGF-induced activation and phosphorylation of PKD were reversed by in vitro incubation of PKD with protein phosphatase 1 or 2A, indicating that PDGF signaling to PKD involves the Ser/Thr phosphorylation of PKD. Taken together, these results conclusively show that PDGF activates PKD through a pathway that involves activation of PLCgamma and, subsequently, protein kinase C.

3T3 Cells↗
PubMed1998

Cell type-specific regulation of CREB gene expression: mutational analysis of CREB promoter activity.

Previous studies have shown that activation of the cyclic AMP (cAMP) pathway down-regulates CREB expression in CATH.a cells, an effect that appears to be mediated via inhibition of CREB gene transcription. In the current study, we compared this effect in CATH.a cells with regulation of CREB expression in another cell line, C6 glioma cells. In contrast to the findings in CATH.a cells, activation of the cAMP pathway up-regulates CREB expression in C6 glioma cells. To determine whether these opposite effects can be explained by regulation of CREB promoter activity, chloramphenicol acetyltransferase (CAT) assays were performed in CATH.a and C6 glioma cells that were transiently transfected with a CREB promoter-CAT fusion plasmid. Activation of the cAMP pathway decreased levels of CAT activity in transfected CATH.a cells but increased CAT activity in transfected C6 glioma cells. We next investigated the effect of mutations in the CREB promoter on such regulation in these two cell lines. Mutations of single CRE or Sp1 binding sites in the CREB promoter reduced basal levels of CAT activity but did not significantly attenuate regulation of the promoter in CATH.a or C6 glioma cells. However, mutation or deletion of two CRE sites in the CREB promoter completely abolished up-regulation of CAT activity in the C6 glioma cells and abolished basal levels of CAT activity in CATH.a cells. CREB promoter activity was also studied in cultured SHSY5Y cells and in primary cultures of striatal neurons as further comparisons. Activation of the cAMP pathway was found to increase CAT activity in both cell types. In the striatal cultures, this effect was obliterated by mutation or deletion of either of the two CREs in the promoter. These findings demonstrate cell type-specific effects of the cAMP pathway on CREB expression, which appear to be mediated via differential regulation of the CREB promoter.

Cell Line↗
PubMed1998

Enhanced magnetic resonance imaging for tissue characterization of liver abnormalities with hepatobiliary contrast agents: an overview of preclinical animal experiments.

Because of the demand for an extension of the range of diagnostic uses for currently available extracellular magnetic resonance imaging (MRI) contrast agents, a new generation of tissue-specific (i.e., hepatobiliary) contrast agents have been successfully developed to enhance the performance of hepatic MRI. These agents include mangafodipir trisodium (formerly manganese dipyridoxal diphosphate [Mn-DPDP]), gadoxetic acid (formerly gadolinium ethoxybenzyl diethylenetriaminopentaacetic acid [Gd-EOB-DTPA]), and gadolinium butylbenzyl diethylenetriaminepentaacetic acid (MS-264). In a series of experiments in animals, the potential of these agents for noninvasive characterization of liver lesions was evaluated with the use of a comprehensive methodology. The purpose of this report was to summarize the observed imaging behaviors of these agents toward different types of cholestasis and focal liver lesions, compare the similarities or dissimilarities of these agents in their possible mechanisms of action, and discuss the clinical implications of the results of the experiments. In summary, through intravenous administration of these agents, both global and local obstructive cholestases can be identified on the postcontrast image. With certain reliability, liver tumors of different origins and grades of cellular differentiation can be detected and classified according to their contrast enhancement patterns occurring at certain postcontrast phases. The invasiveness or degree of a malignancy of the liver tumor can also be suggested by the presence or absence of a peritumoral rim sign. Such diagnostic information, otherwise only invasively achievable, may prove to be invaluable in clinical decision making.

Animals↗
PubMed1998

[A study on the distribution and etiology of pathogenic vibrio in the 5 coastal provinces of China].

In order to understand the distribution and pathogenicity of vibrio in the coastal areas of China a study consisted of 51 water samples and foodstuff from 10 different areas in 5 provinces was conducted microbiologically and etiologically. Results showed that 45 pathogenic vibrio were identified, with majority of A. caviae (26.7%), V. alginolyticus (22.2%) and V. parahaemolyticus (11.1%), same kinds of vibrio found in feces from patients with acute infectious diarrhea. Prevalence rates of pathogenic vibrio identified from the East China Sea, the South China Sea and the Yellow Sea were between 66%-77%. The detection rate of pathogenic vibrio in 29 water samples was 93.1% (27/29) with 38 strains isolated mainly in river water (57.8%), followed by in sea water (21.1%) and pool water (21.1%). The results revealed that the distribution of pathogenic vibrio in different waters was closely related to its pathogenecity, providing evidence that vibrio diarrhea be supervised, diagnosed and treated in order to decrease the incidence of the disease.

China↗
PubMed1998

[Studies on dynamic changes of SOD and MDA in cultured cells from Schistosoma japonicum schistosomula].

AIM: To observe the dynamic changes of superoxide dismutase(SOD) and maldondialdehyde(MDA) in cultured cells from Schistosoma japonicum schistosomula and to explore the degeneration process of cultured cells. METHODS: Pyrogallol method and thiobarbituric acid method were used to determinate the levels of SOD and MDA, respectively, in the cells cultured for 0-54 days. RESULTS: SOD in the cells reached a peak level on d12 of the early stage of culture and then decreased. The MDA levels in the cultures cells ascended gradually, and had two peaks on d18 and d48, during the period of culture. CONCLUSION: The cultured cells from S. japonicum schistosomula degenerated progressively.

Animals↗
PubMed1998

[Determination of net analyte emission intensity and signal-background ratio of Mg, Cr, Cd and Mn in Ar-air mixed coolant gas ICP].

The dependence of net analyte emission intensity and signal-background ratio on coolant gas composition and observation heights for 8 lines of four elements (Mg, Cr, Cd and Mn) in Ar-air mixed coolant gas ICP was measured under the similar condition as that in the low power Ar-ICP with a commercial sequential plasma spectrometer. Further, the detection limits under compromise conditions were estimated. The results show that ion lines and neutral atom lines with high excitation energy have maximum intensity and are more intense than those in the Ar-ICP, when 5-10% air is added to the coolant flow. The intensity of neutral atom lines with low excitation energy drops gradually as air is added to coolant flow. The signal-background ratio of analyte lines depends upon excitation energy and wavelength.

English Abstract↗